Well bore treatment



Jan. 9, 1940. D, c. MATTHEWS 2,186,375

` WELL BORE TREATMENT Filed June 27, 1938 2 Sheets-Sheet l VI infr] mmllllfLLulf iw if) DUKE C. MATTHEWS Jan. 9, 1940. D Q MATTHEWS 2,186,875

WELL BORE TREATMENT Filed June 27, 1938 2 Sheets-Sheet 2 agay. 62

wuc/rvbo'o DUKE C`. MATTHEWS il Nimm/m Patented 9,

UNITED Asiiirrlas PATENT OFFICE 'wsu noaa 'TREATMENT Duke C. Matthews, yTaylor, Tex. application .im s1', issaserisi No. 216,111A z Claims. (ci. 1st-21) This invention relates to the art of well'drilling, land particularly to the treatment of well bores at various stages of a drilling operation. l

In the drilling of oil wells it often happens that porous formations, or crevice strata. are -encounterei'l. Usually such formations or strata offer such low resistance to penetrating action of the well fluid or mud that thel fluid is diverted from the well bore and is lost to an extent sumcient to cut oif or partially check proper circulation of the well fluid. v Under such conditions it has been the practice in the art to seal off such formations or strata byintroducing a well sealing compound into the bore and forcing it into the lateral area to be sealed, so that proper circulation anddrilly ing may be continued.

However, the sealing thuseifected is of a permanent character, and is accordingly unsuitable 'to conditions in which the presence of oil or gas is indicated or suspected in the crevice area or porous formation, and to which it is desired to set a well casing.

It is, therefore, an object of this invention to provide a method .of temporarily plugging a crevice stratum or porous formation lagainst loss of well fluid or cementing material while setting a well casing thereto, without permanently altering the character ofthe formation or stratum. l e y v. l -Under certain conditions of drilling itis de-y sirable and necessary to make drilistemtests of crevices and porous formations, or to seat a cas- Lingat such crevices or formations. In such operations the presence of a drill stem or casing'seatl l is necessary,'esp`ecially in-lrge bores.

Accordingly, another object ofthe invention is to provide a methodof temporarily blocking such crevices or porous formations against entry of a plastic setting material used .in forming the re- U quired seat, without alteration or injury tothe physical character of the formations or crevice` areas.

Still another object is to provide a method of physically andtemporarily sealing a well bore 4I crevice or porous formation by a soluble medium capable of only temporarily supporting at itssurface a superimposed column of a plastic setting material, the physical character of the supporting medium changing automatically after th 50 plastiesetting material has hardened.

p Other objects will be readily apparent to those skilled in the art. l

In the accompanying drawings, wherein like characters of reference designate like parts throughout the several views:

Figure 1 is a vertical section through a well bore illustrating a step in the method of temporarily blocking oif a porous formation or crevice while cementing a Well casing.

Figure' 2 is a similar View illustrating anotheri step in the same method.

Figure 3 is a horizontal section taken on the vline 3 3 of Figure 2.

Figure 4 is a vertical section through a well bore .illustrating a step in the method of tem. l0 porarily blocking off a porous formation or crev ice while .forming an artificial seat for a well casing or drill stem test.

Figure 5 is a similar view of a subsequent step in forming the seat.' A f 4 1 Figure 6 is a similar view illustrating a further Vsubsequent step in formation of the seat.

Figure? is a horizontal section taken on the line 1-1 ofgFigure l6.

'In Figures 1 and-2 the well bore 8 has been 20 vdrilled to a stratum 9 which may be-of porous character sufllcient to permit ready seepage therethrough of the conventional weil fluid, or which may contain lateral crevices I0, or both, and in which the presence of oil or gas is indicated or suspected. Under such` conditions the leakage of thel well fluid impairs circulation and in many casescuts it oifentirely. Due to thepossibility of encountering gas or oil it becomes'necessary v to case the well to that point, [and in accord- $0 ance with usual practice the. casing must be cemented above v the producing stratum. ,'How ever, the porosityof the formation or the crevices would take up'the cement unless sealed, but 4 Y if permanently sealed the1 stratum may berengs dered non-productive. l

In the practice of the method of this invention the bottom of the well bore is tilledfromits bottom to a level above the top of the stratum I with a soluble compound pumped into the bore 40 through the drill stem. 'I'he compound employed is of the type disclosed in United States Patent No. 1,998,756 and is a product that may be obtained on the open market. It is soluble,

and in its liquid form is pumped into the bore and gg allowedl to settle on the bottom where it soon forms Y,

a heavy, thick agglutinate mass I2 'which fills the crevices I0 and seals the pores of the formation. When the mass of `agglutinate compound I2 v has had time to thicken a. cas.ng Il is run to a Point somewhere above the surface of the 'agl glutinate, as shown in Figure 2, and cement is pumped down through the casing. When the agglutinate compound has thickened it becomes resistant to 'the .passage of iiuid and has a 5s 2 A aisasvs strength amply sufficient to support the full weight of a column of the cement Il or well fluid I5. In practice. the well uuid IB is pumped following settling of the agglutinate i2 until free cir- 5 culation is obtained, after which the casing I3 '-is run to the desired point. When the casing is in position the cement is pumped in and is forced up behind the casing as a column Il supported directly on the top of the agglutinate sealing mass i 2 or slightly thereabove in the event a small body of intervening fluid separates the cement from vthe sealing mass. In those cases where the time for running a casing is short, the drill stem may nrst be removed and the casing run to the desired point, after which the agglutinate compound may be pumped down through the casing itself.

The compound I2 is of such character that it automatically liqueiles after it has reached its maximum density. However. the llquefactlon time is such that before the compound becomes sulciently liquid to no longer support the column II the cement will have set and become fully hardened in situ. Upon liquefaction of the compound I2 it is easily removable by pumping, and thus uncovers the crevices and pores of the stratum 8 which it has temporarily sealed. 'I'he physical character of the formation is unaltered by the temporary sealing, so that operations m'ay be continued for bringing in the well if the stratum 8 is a producing level. If it proves not to be, the stratum may be sealed oif in accordance with the conventional practice and the drilling may then be continued to lower depths.

The method of locating and forming an artificial seat for a well casing or a drill stem. test is shown in Figures 4 to 7, in which the bore 8 has entered strata 9' of porous formation or con- 40 taining crevices I0' through which the well uid passes away or is absorbed so rapidly as to interrupt its proper circulation, and which would with equal facility absorb or divert cement.

As in the preceding method, the lower part 0f 5 the well bore is filled with a mass of the agglutinating compound l2 until it rises to the top of the objectionable stratum or formation, being pumped in through the stem Il and allowed to settle at the bottom of the bore. In due course the compound thickens to a density and consistency which effectively plugs up the crevices and pores of the formation, and which is of sumclent strength to suport a column of cement Il' which is pumped into the well bore to a desired height.

The compound forming the agglutinate mass I2 automatically liquees after reaching its maximum thickness. but before it liqueflea to the point at which it is incapable of further supporting the weight of the cement column the cement will have set and become fully hardened in situ, forming a seat for a casing or for a drill stem test of the formation. 'I'he hardened cement body I 4' forming the seat is then drilled to provide a bore I6 extending therethrough and through which the test can be made in the usual 10 manner of such operations.

While certain specific applications of the method have been disclosed herein it is to be understood that the invention is capable of practice in other ways and for other purposes. 15

Having thus described the invention, what is I claimed is:

1. Inv a well drilling operation, the method of forming a body of plastic setting material in situ in a well bore above an uncased portion into N which such material would normally dissipate while in a plastic state; which comprises filling the bore througcut such portion with a liqueed compound which on standing forms into a thick agglutinate incapable of dissipation into said well $5 bore portion and capable of supporting on its surface a body of the plastic setting material, and which subsequently resolves to liquid state after a longer time than the plastic setting material takes to set; and after the compound has l0 thickened disposing on its surface a body of plastic setting material in a plastic state and allowing it to set into desired form.

2. In a well drilling operation, the method of -cementing a casing above a porous formation or 5 stratum which freely absorbs and dissipates well fluid and plastic cement, and which it is not .desired to seal off, which comprises the steps of filling the well bore throughout such formation with a iiowable compound which forms into a w thick agglutinate incapable of dissipation into the formation and capable of supporting o'n its surface a body of cement and which subsequently resolves to liquid state after a. longer time than the cement takes to set, placing a casing in the 45 well bore with its lower end spaced somewhat above the surface of said compound, introducing cement through the casing onto the surface of the agglutlnated compoundand forcing the cement upwardly in the bore around the casing exso terior, allowing the cement to harden in situ. and, when the agglutinate has resolved to liquid state, removing it from the well bore through the casing.

DUKE C. MATTHEWS. 

